No definition found for GetActiveObject from System.Runtime.InteropServices.Marshal C#

Question

I'm trying to connect to a running Excel instance, but when I try to use the following code snippet:

using Microsoft.Office.Interop.Excel;
using System.Runtime.InteropServices;

public Application StartExcel()
{
    Application instance = null;
    try
    {
        instance = (Application)Marshal.GetActiveObject("Excel.Application");
    }
    catch (COMException ex)
    {
        instance = new ApplicationClass();
    }

    return instance;
}

I found similar snippets on the internet, but when I compile this code I get the following error:

error CS0117: 'Marshal' does not contain a definition for 'GetActiveObject'.

I do not know why, because I have the following NuGet packages: - Microsoft.Office.Interop.Excel - System.Runtime.InteropServices

You used the wrong project template to get started. It can't be a .NETCore project, must be .NETFramework. Which is fine, you need Windows anyway to run Excel and this code. Give .NETCore v3.0 at least a couple of months to get stable. — Hans Passant, Sep 19 '19 at 13:03

score 20 · Answer 1 · answered Dec 29 '20 at 17:32

We need to pull the GetActiveObject(String ProgID) function from the source code GitHub.Microsoft

Create your own class, for example - Marshal2

And use as before

Marshal2.GetActiveObject(progID);

Source code

public static class Marshal2
{
    internal const String OLEAUT32 = "oleaut32.dll";
    internal const String OLE32 = "ole32.dll";

    [System.Security.SecurityCritical]  // auto-generated_required
    public static Object GetActiveObject(String progID)
    {
        Object obj = null;
        Guid clsid;

        // Call CLSIDFromProgIDEx first then fall back on CLSIDFromProgID if
        // CLSIDFromProgIDEx doesn't exist.
        try
        {
            CLSIDFromProgIDEx(progID, out clsid);
        }
        //            catch
        catch (Exception)
        {
            CLSIDFromProgID(progID, out clsid);
        }

        GetActiveObject(ref clsid, IntPtr.Zero, out obj);
        return obj;
    }

    //[DllImport(Microsoft.Win32.Win32Native.OLE32, PreserveSig = false)]
    [DllImport(OLE32, PreserveSig = false)]
    [ResourceExposure(ResourceScope.None)]
    [SuppressUnmanagedCodeSecurity]
    [System.Security.SecurityCritical]  // auto-generated
    private static extern void CLSIDFromProgIDEx([MarshalAs(UnmanagedType.LPWStr)] String progId, out Guid clsid);

    //[DllImport(Microsoft.Win32.Win32Native.OLE32, PreserveSig = false)]
    [DllImport(OLE32, PreserveSig = false)]
    [ResourceExposure(ResourceScope.None)]
    [SuppressUnmanagedCodeSecurity]
    [System.Security.SecurityCritical]  // auto-generated
    private static extern void CLSIDFromProgID([MarshalAs(UnmanagedType.LPWStr)] String progId, out Guid clsid);

    //[DllImport(Microsoft.Win32.Win32Native.OLEAUT32, PreserveSig = false)]
    [DllImport(OLEAUT32, PreserveSig = false)]
    [ResourceExposure(ResourceScope.None)]
    [SuppressUnmanagedCodeSecurity]
    [System.Security.SecurityCritical]  // auto-generated
    private static extern void GetActiveObject(ref Guid rclsid, IntPtr reserved, [MarshalAs(UnmanagedType.Interface)] out Object ppunk);

}

I don't know why this is not the accepted answer. This works. I tried it with .NET 5.0 — Olivier Jacot-Descombes, Jan 25 '21 at 19:56
Worked for me. But I had to open the application as the Administrator. — James Lawruk, Nov 09 '21 at 13:59

score 3 · Accepted Answer · answered Sep 19 '19 at 12:19

3

This is available only .Net Framework but not for .Net Core . Please check the .Net project type .

https://docs.microsoft.com/en-us/dotnet/api/system.runtime.interopservices.marshal.getactiveobject?view=netframework-4.8&viewFallbackFrom=netcore-2.2

answered Sep 19 '19 at 12:19

GowriPranithBayyana

1,595
1
10
21

I'm quite new to the C world in total, does that mean I have to create a new project or ...? – Patrick.H Sep 19 '19 at 12:21
Yes . You may have to create a new project targeting .Net Framework instead of .Net Core . – GowriPranithBayyana Sep 19 '19 at 15:29

No definition found for GetActiveObject from System.Runtime.InteropServices.Marshal C#

2 Answers2

Linked

Related